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Abstract: Synthetic herbivore-induced plant volatiles (HIPVs) attract arthropod natural enemies showing potential for enhancing biological control. However, HIPVs can also affect the behavior of arthropod herbivores and possibly higher-order natural enemies, potentially complicating the use of HIPVs in biological control. The aim of our work is to understand the effects of one HIPV on the abundance of arthropods at three trophic levels. Of particular interest are effects on herbivores and enemies of natural enemies. A field experiment was carried out in turnip Brassica rapa L. (Brassicaceae) (cv. Green Globe). A randomized block design was used with a treatment of synthetic methyl salicylate (MeSA), and a control consisting of the crop alone. Yellow sticky traps were used for sampling aerial brassica pests, their natural enemies and fourth trophic-level natural enemies within the crop. Our results showed that the abundance of the diamondback moth parasitoid, Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae), the brassica leafmining pest Scaptomyza flava Fallén (Diptera: Drosophilidae), and the lacewing parasitoid, Anacharis zealandica Ashmead (Hymenoptera: Figitidae), increased significantly in the MeSA-treatment compared with the controls. Significantly more D. semiclausum females were attracted to MeSA than were males. However, it still remains unclear whether it is MeSA and/or volatiles produced by induced host plants that are attractive to the arthropods. These results are highly relevant to potential future application of HIPVs in pest management, as the attraction of arthropods within ‘untargeted’ trophic-levels may disrupt trophic cascades and challenges the ideas that the deployment of synthetic HIPVs in pest management may enhance biological control. [Copyright &y& Elsevier]

Herbivore plant damage induces emissions of semiochemicals termed herbivore-induced plant volatiles (HIPVs). These volatile cues can attract the natural enemies of the attacking herbivores and protect the plant from further damage. Synthetic HIPV application to various crops has also been shown to attract natural enemies. In the present study, nectar plant rewards were combined with HIPVs in an 'attract and reward' approach. This combination might attract natural enemies into treated crops and provide them with food and shelter to maximise their survival and residency leading to increased parasitism and lower pest abundance. Trap catches of predators and scelionid parasitoids in treated grapevines were increased by methyl salicylate (MeSA) and methyl anthranilate (MeA) for 1 day and up to 5 days, respectively. The number of herbivorous thrips was also increased for up to 3 days post-treatment. Buckwheat ( Fagopyrum esculentum) reward increased catches of eulophid parasitoids and thrips over the 28-day experiment. These results suggest that 'attract' and 'reward' can separately enhance local abundance of natural enemies but further work is required to fully realise the potential for synergistic effects. [ABSTRACT FROM AUTHOR]